Japanese Patent No. 57,745 (1982) discloses epoxy resins containing dispersed polymer produced by copolymerization of isocyanate-polyol prepolymer addition products of hydroxyacrylates and other ethylenically unsaturated monomers as well as cured compositions thereof. Said modified epoxy resins are produced by adding isocyanate-polyol prepolymer addition prcducts of hydroxyacrylates and other ethylenically unsaturated monomers to epoxy resin and then copolymerizing therein. Although said compositions containing a polymer dispersed in the epoxy resin provide improved adhesion, the dispersed polymer is not chemically bonded to the epoxy resin backbone and is thus susceptible to migration or extraction from the cured resin.
U.S. Pat. Nos. 3,297,745 and 4,390,662 disclose the copolymerization of mixtures of vinyl ester resins (vinyl ester plus ethylenically unsaturated monomer such as styrene) and vinyl terminated urethane oligomers. The vinyl ester compositions of the aforesaid inventions do not possess polymer modificalion, that is, the vinyl terminated urethane oligomer and optional polymerizable ethylenically unsaturated compound are not chemically bonded to the precursor epoxy resin backbone.
The present invention provides novel polymer modified epoxy resin compositions produced by copolymerization of an epoxy resin containing polymerizable ethylenic unsaturation and a vinyl terminated urethane oligomer and, optionally, a polymerizable ethylenically unsaturated compound.
An additional embodiment of the present invention pertains to cured polymer modified epoxy resin compositions.
A further embodiment of the present invention pertains to polymer modified vinyl esters produced by reaction of the aforesaid polymer modified epoxy resin and a monounsaturated monocarboxylic acid.
An additional embodiment of the present invention pertains to cured polymer modified vinyl esters and vinyl ester resin (vinyl ester plus polymerizable ethylenically unsaturated monomer such as styrene) compositions.
Both the polymer modified epoxy resins and vinyl ester resins of the present invention provide cured compositions with enhanced properties such as tensile strength, elongation, ductility or the like while largely retaining the other mechanical properties. Furthermore, said compositions are not susceptible to mechanical property losses due to extraction or migration of the polymerized vinyl terminated urethane oligomer component, since it is at least partially chemically bonded to the epoxy resin backbone. Furthermore, the total or partial chemical bonding (grafting) of the vinyl terminated urethane oligomer and polymerizable ethylenically unsaturated compound, if any, provides epoxy resin compositions with generally enhanced mechanical properties relative to the prior art epoxy resins containing only a dispersed polymer phase. This is due to compatibilization induced by the aforementioned grafted epoxy resin component(s). As an added benefit, the polymer modified vinyl ester resin compositions of the present invention do not require a separate addition and blending step for the vinyl terminated urethane oligomer component and its overall compatibility (i.e. degree of phase separation) is more easily controlled.